Donnelly MSO 650B X 50mm: At The Finish

Donnelly MSO 650B X 50mm: At The Finish- by Grannygear

Editor’s Note: Please click here for the “Checkpoint” post previous to this final verdict on the MSO tires.

I get sea sick.  I just wanted to toss that out there (no pun intended), so when I had an offer to stay on a friend’s sailboat for the weekend and do some riding on Santa Catalina Island, an island 26 miles off the Southern California Coast, I decided to take the 45 minute crossing on the high speed catamaran (Catalina Express) over to see them rather than the slow and wobbly 4 hours it takes to get there on their sailboat.  That also let me bring a bike, basically rolling it on board the ‘ferry’, along with a bag or two.

Donnelly 650B X 50mm tires on Grannygear's Lynskey
The MSO in 650B X 50mm size as seen on Grannygear’s Lynskey

But what bike should I bring?  Last time I took a Plus bike hardtail and that was too slow.  The roads there are not very rough, but the climbs seem never ending and are often quite steep.  I recall thinking that this would be a great gravel bike destination.  And so it was settled.  I decided to keep the MSOs on the Lynskey even though I would be paying a bit of a weight penalty with all that climbing.  However, in trade I would be bombproof on any rough parts, would be crushing the fast downhills, and overall comfort would be as good as it gets.

Honestly I could not have made a better choice.  In the dirt, I did not notice the rolling weight really, and the comfort and capabilities of the 50mm casing were so reassuring that it reaffirmed how valid this set up would be for any backcountry use like bikepacking, etc.

At the end of the day, I could have run my standard 700×42 Resolutes and been fine, but with no pavement except one small part (and that was horrible pavement actually), I gained more than I lost with the 650Bx50 setup.

Grannygear's bike at the Catalina Island conservancy sign.
The MSO’s took Grannygear to some spectacular places.

Now that this is a wrap, what are my specific thoughts on this tire and the 650B category et al?  I am glad you asked.
First, the Donnelly MSO Xplor 650Bx50 Good and the Less Than Good:

  • I enjoyed the rugged nature of the MSO casing and never felt like I was going to hurt the tire.  And I never did.  I ended up running around 25psi a lot of the time, 30psi tops.
  • The MSO sealed up like a clam, never hinting at any sealant weeping.
  • The rolling performance on smooth surfaces is very good.  Yes, it is heavy-ish, but once up to speed, you would never know that.
  • I never tried to push it really hard in dirt corners and those are not aggressive knobs, so I would only expect so much.  But it puts a lot of rubber on the ground, so for the limits of a gravel bike at least, I found the cornering ability to be fine.
  • It was very hard to keep the rear tire hooked up if I was climbing out of the saddle while standing and I was on a sand/gravel over hardback surface.  That center tread is pretty ridge-like.  It would quite easily let go and spin.  
  • On paved roads and while cornering, the tire would give off this ‘squidgy’ sound like the knobs were squirming around.  Not sure if it really hurt anything, and the tire was never scary or anything, but it sounded odd, like cornering on an octopus.  It is not a road tire, so I will give it some slack here.  I expect any gravel ready tire with this size casing will end up feeling a bit vague and bouncy in tight, sweeping corners on pavement and at speed.  It’s just too much volume and sidewall.
Overlook on Catalina Island looking at a harbor filled with sailing vessels.

After quite a few rides on this tire, I had a 30 mile ride coming up and I had another decision to make.  The ride was 2/3 pavement and featured a 10 mile, relatively smooth dirt climb, so while the MSOs would have been OK, for this ride I swapped back to my Rolf Prima wheels with the 42mm WTB Resolutes.  The difference was pretty striking.  On the road, I much preferred the 700c combo, not just for speed, but that shorter sidewall allowed for much more tire support in corners. The bigger casing of the MSO was bouncier and less inspiring on fast road sweepers and hairpins. I also noted how the bigger wheel felt like it wanted to slow down less on chattery areas and stutter bumps.  It felt snappier on anything that went uphill as well.  

But I also lost a lot of that casual approach to corners, ruts, etc, that the 650Bx50 engenders.  I ‘re-tuned’ to the 700c wheel and smaller tire, but it took a bit of time.

So what to think about 650B in this bigger tire size, that being a 50mm/2.0? If I were constantly in rough dirt I think I would run 100% of the time with the MSO Xplor.  The worse the road, the better this tire is.  However, it has precious little side knobs and a compacted tread, so traction on off camber ruts and such will reach a limit at some point.  A 650B setup also ‘quickens’ the handling of any bike designed around a 700c wheel so there is a bit of an agility gain here.  It does feel a bit ‘moto’, if that even applies to a gravel bike.  As you get onto more moderate dirt roads/smoother gravel mixed with pavement, then either wheel and tire size is OK and it comes down to preference.  And as the sliding scale moves more toward even smoother dirt and road use, I prefer the bigger rolling presence, lighter weight, and firmer cornering tire of the 700c wheel.

The 650B X 50mm Mso with a cactus background

The 47mm size in a 650B is a bit of a tweener here.  My times on a WTB Horizon are always enjoyable and I would run them for bikepacking/light touring if I were running mostly road mixed with decent gravel or dirt.  They actually make a convincing argument for all-round, all of the time use being pretty darn fast on the road, but that bigger casing can feel bouncy and odd at times on faster pavement corners.  650Bx47mm is also a size that fits a lot of bikes so that is a win.

But this 650B in the 50mm/2.0” size is next level stuff, more like a small MTB tire, which it kind of is.  And that bump to the bigger casing brings with it a whole bunch of WHEEEE!!! and other great things when the road ahead barely looks like a road or the trail gets sketchy.  It’s good fun in a situation where less tire would be less fun.  And we do want to have fun when we ride unless we are a triathlete or one of those RAAM persons, then not so much :).  

The catch?  It’s too big for most bikes on the market and will not fit in their rear triangles.  But that might be changing as more bikes, like the new V4 Salsa Warbird, will run a 2.0”x27.5” (650B) tire and up to a 45mm 700c set-up.  I am not sure this is the way all bikes should go (and it seems to be easier to do it in carbon if you care about 2x capabilities…’tube’ shaping, etc) but any bike with pretenses of being a strong contender in gravel/exploration better be ready for this capability.  

Bottom bracket height is a bit of a caution though.  I bike with a lot of bottom bracket drop that was designed around a 700x38mm and bigger tire could be a bad deal if you convert to a 650Bx47mm combo.  I bet many folks will try this even when many manufacturers do not suggest it.  I have read of persons doing this on the new Specialized Diverge but that frame has 85mm of bottom bracket drop!  That is a LOT!  Pedals will be getting very close to the ground with a wheel downsize.  “Danger, Will Robinson!”  And I would say that any bike designed to run both wheel sizes is a bit of a compromise.  I doubt that the amount of trail designed into a geometry that is best for the smaller wheel and tire (not to mention the increased tread width) is also the best trail number and geometry for a 700cX42mm wheel and tire.  Or bottom bracket drop. Or maybe even chain stay length.  Just sayin’.  But I imagine the compromise is small enough to absorb it as we ride and tune into the bike after wheel swaps.

All that said, I really like this Donnelly MSO Xplor and it will stay in my garage as a keeper for those days where the ride calls for ‘more’.  For me, it validated this wheel/tire combo as being important and viable and I am glad that my Lynskey is capable of running both setups.  For where I live it makes sense and gives me options.

And options are good things to have.

NOTE: Donnelly sent over the MSO 650B X 50mm tires at no cost to for test and review. We were not bribed, nor paid, for this review and we will always strive to give our honest thoughts and opinions throughout.



About The Author: Grannygear hails from SoCal and spent most of his cycling days as a mountain biker from the formative years of mountain biking all the way up to the present day. His day job is in the tech sector, but he has spent time writing about off road 4X4’s, 29″ mountain bikes, and cycling in general. Grannygear and Guitar Ted have worked off and on together since 2009 after a chance meeting at Interbike. With gravel cycling on the rise, Grannygear has been exploring how this genre’ works in SoCal and now does guest pieces for in his spare time.



Author: Guitar Ted

Guitar Ted hails from Iowa. Home of over 70,000 miles of gravel and back roads. An inaugural member of the Gravel Cycling Hall of Fame and Co-creator of Trans Iowa in late 2004- Guitar Ted has been at the forefront of the growth of gravel events and riding since then. Creator of Gravel Grinder News in 2008, he produced the premier calendar of gravel and back road events. GT joined forces with Riding Gravel in late 2014.

Related Articles

13 thoughts on “Donnelly MSO 650B X 50mm: At The Finish

  1. I was recently watching a web video titled “Top 5-2019 Gravel Bikes” and I was suprised to see that one of the Top Picks was ” any XC Hardtail”. I have a 29+ hardtail with i35mm rims. So I mounted up a set of 700×50 Gravel tires at 20psi but I didn’t think it would work well. Shockingly, it worked very well—very fast on both pavement and gravel and also very comfortable. The tire wasn’t adversely affected by such a wide rim and in fact, I think it might make the tire work better. I have to wonder if the 50mm X’plor’s would have worked better on a wider rim. I’m not saying that 50mm tires need i35 rims but maybe something like an i27-29 rim might be good. Anyway, I like my Gravel Hardtail better than my old Crossbike with 35mm tires. The wider tires are just much more enjoyable even if they are not as fast on pavement. However, the 50mm tires are faster than the 35mm tires on gravel.

    I think the XC Hardtail with Gravel tires deserves serious consideration. Most XC Hardtails come with i25 rims. If I extrapolate, a 40mm tire would work well with an i25 rim (a 45mm tire with an i30 rim). An XC Hardtail with 40mm tires would be very fast.

    If you’re a Mountain biker at heart who prefers front suspension, flat bars, and mountain geometry, a Hardtail with Gravel tires might be the Gravelbike for you. Or if you have a Hardtail and are curious what this Gravelbike trend is all about, mount up some Gravel tires. I think you will like it!

  2. @Bike Nerd…I would add a couple of observations. Of course you can ride a XC hardtail on gravel. Why not? But it’s not a gravel bike. At some point the lack of hand positions will be ugly and tiring and the riding position is most likely too upright. And you are dragging around the weight of a sus fork that is not needed and a frame that is overbuilt for the task at hand. The geometry would be tweaked for technical riding that no maintained gravel road would present to you. I am not sure if wider rims are that important, even with a 50mm tire on gravel, although it would not hurt anything. And 29mm might be a sweet spot. You are adding wheel weight though. You could drop the tire pressure even lower and that is what wide rims on MTBs are so good for…lower PSI with tire support intact, but on a bike that I use on pavement too…how low do I go?

    I don’t think that “the XC Hardtail with Gravel tires deserves serious consideration” unless you just happen to have one and want to go riding. Mountain Bikes are great at mountain biking. And Gravel Bikes are great on gravel roads.

    My thoughts, anyway.


    1. @gg…Don’t knock it until you try it. Get one of the bike companies to loan you a decent XC Hardtail and put on some Gravel tires say 42mm and give it a test ride. Many Gravelbikes aren’t that light-weight and some even come with suspension. Even better, get a 29 XC Hardtail and a 700 Gravelbike in the same price range say $2500 and put identical tires on both bikes and have a shoot-out. If your experience is like mine, the XC Hardtail with Gravel tires is going to turn out to be way better than you think it will be. I’ll admit that the Gravel Hardtail might not be as fast on pavement but I think you will find it more comfortable. And on dirt the Gravel Hardtail will be just as fast but also more capable when the going gets rough.

      1. I did it (the 40 MSO on a 29er hardtail).

        It was no gravel bike! It was just a slightly more adept hybrid bike. The truth to what it was, revealed itself as soon as I put MTB tires back on the hardtail. If the hardtail was to enter a gravel race or fast paced gravel ride of distance then I’d throw the 29 x2.1 Nano’s on it. not the 700x40c gravel Nano tires.

        I since put the 40 MSO on a gravel bike and there is no comparison that a gravel bike is hands down better for gravel riding.

        This is coming from the guy that Really missed my hybrid bike, so rebuilt a 90’s hybrid. due their rigid forks, and more aggressive geometries than the new hybrids. not it will run the Gravel tires, but it’s short comings is the flat bar. maybe it needs a Jones bar, but that’s not going to be aggressive fast paced riding either.

        bottom line, there will be a “pace” for everyone. If your gravel tire on a XC hardtail works for you then that’s you.

  3. @Bike Nerd…I have done the Crusher in the Tushar on a light XC 29er HT with 1.8s and on a Salsa Warbird with 40s. I have done Rebecca’s Private Idaho on a Specialized Epic with 2.0s and on three different gravel bikes with 38s to 42s. So I do know how it is. I stand by my post comments. It’s doable, but not optimal.

    Honestly if I WAS going to go to a 29er for something like that again, I would do it on a racy, short travel, light (as in expensive) FS 29er. If you are going to have the wrong handlebar, so-so geometry for gravel races, and that big old sus fork on there, you might as well be comfy at both ends.


  4. @ gg and Tim…Thanks for responding to my comments. I’ve owned Roadbikes or Crossbikes for 45+ years. My experience of Roadbikes is that I was making fast time but I wasn’t having a good time. The ride is stiff, twitchy, and riding in the aero position is uncomfortable and I really don’ t enjoy riding in traffic. I sure am glad that Mountainbikes were invented because otherwise I would have given up on bikes all together. The Crossbike was a bit better but 35mm Cross tires on 15mm Road rims was only a mild improvement and it really wasn’t much fun on gravel—to stiff, sketchie, and unstable. So my Crossbike ended up being my wide tire roadbike which I mostly ride in the winter when the singletrack is unrideable. In addition, I’ve never liked drop bars. I seldom use the drops—so I’m not riding in a very aero position anyway. And reaching forward to use the brakes or shift makes no sense to me. I want my weight back when I brake or the going gets rough or steep. That’s been my experience of drop bar bikes before Gravelbikes came out.

    So here comes this new type of bike called a Gravelbike which has a lot of potential but seems to be dominated by a drop bar Roadie mentality where all that matters is being fast with comfort and stability a distant second. Not that I have anything against being fast but I’m willing to give up a little speed to make it more enjoyable. I guess I’m more of the wider 40-50mm tire Touring Gravel rider than the narrower 30-40mm tire Racing Gravel rider. So what does the Gravelbike industry have for me? Almost no Gravelbikes come with flat bars. Very few 700c Gravelbikes have clearance for tires wider than 42mm. To use tires wider than 42mm, a 650b Gravelbike is required. However, the 650b wheels are just patched onto 700c bikes—the bikes are not actually designed for 650b wheels. And I’ve never liked smaller 650b wheels much anyway. So where are the Gravelbikes that are designed for 700×40-50mm tires. The tires are out there but there are just no bikes. If someone would make a high-quality flat-bar Gravelbike with clearance for 700×40-50mm tires I would buy it. In the meantime, I’ll stick to my Hardtail Gravelbike. Not because I think it is the best Gravelbike out here, but because I don’t have any other options. And I’ve got to say, “I’m having fun riding my Hardtail Gravelbike”. Do a web search of “hardtail vs gravel” and you’ll find that I’m not the only one who feels this way.

    1. Of course you can ride an MTB on gravel. 🙂 Nothing new here dude. You don’t even need gravel tyres, an XC 2.2-2.3 can be just as fast and just as light. You haven’t invented anything by riding a bike offroad that was designed to be ridden offroad. 🙂

      A “flat bar gravelbike with clearance for 700×40-50mm tires” is called a hybrid or trekking.

      To me the most important thing on a gravel bike is the drop bar. Doesn’t matter what kind of bike it is, how expensive it is, I can’t do flat bars over long distances, and I envy those who can.

  5. How wide did these end up being? And on which rim width and what pressure was that width measured?

  6. Hi Ted,

    What are your thoughts of this tire fitting in the back of a raleigh roker comp in the 650bx50 size. Seeking a strong one that can tackle single track. If not this one any suggestions?

    Thanks so much! Stay Healthy!

    1. @Mike Geffen – The 650B X 47mm Horizons and their ilk barely clear in a steel Raleigh Tamland and as I recall, the Roker carbon bikes have less clearance than the Tamlands did. My guess is no, that tire won’t fit. At least not with any acceptable clearance.

      1. Not sure about that as I have had bike shops say a 2.1 would clear in the single chainring roker in a 27.5 at least up front. I was told 2.0 in rear but not sure about that. The roker is meant to handle a 45 in a 700. My Roker came with 700 clement’s x 40 and still lots of room. You may have not seen the last part of my question above as no suggestions were made. Thanks in advance.

        1. @Mike Geffen – One has to wonder, “What is acceptable clearances for tires?” Sure, a tire may spin freely at a given size, but is there any room for trail debris/gravel/grit to pass? I got 29X2.0’s to ‘spin” in my Tamland Two, but there is no way I would have ridden them on a gravel road.

          Single track capability. Again- too many variables to offer any cogent advice. Your trails, riding style, and more come into play there. I know guys back in the 90’s who were cleaning up at XC MTB races on cyclo cross bikes with 90’s era tubulars. I know trails where anything less than a 2.5″ tire would be insanity. Rider skills, conditions….Yeah. No way I can give you any sort of answer without a ton more fine detail.

Leave a Reply

Your email address will not be published.